Backing up virtual machines in Hyper-V: theory question

Question

Hello!
This article http://msdn.microsoft.com/en-us/library/dd405549%28v=vs.85%29.aspx says:
"Hyper-V uses the Volume Shadow Copy Service (VSS) to backup and restore virtual machines (VMs).
If the backup (volume snapshot) integration services are installed in the guest operating system, a VSS requester is installed that will allow VSS writers in the guest operating system to participate in the backup of the VM. "
Backing Up the Virtual Machines
Hyper-V uses one of two mechanisms to back up each VM. The default backup mechanism is called the "Saved State" method, where the VM is put into a saved state during the processing of the PrepareForSnapshot event,snapshots
are taken of the appropriate volumes, and the VM is returned to the previous state during the processing of the PostSnapshot event."
The other backup mechanism is called the "Child VM Snapshot" method, which uses VSS inside the child VM to participate in the backup....
Backup (volume snapshot) Integration Service is installed and running in the child VM.
The child VM must be in the running state."
Putting it all together: the backup integration services are installed in the guest operating systems by default (at least in Win2008-2012R2), but "The default backup mechanism is called the "Saved State" method,...",
wich does NOT use child vm snapshot creation. It means that checking the "Backup (volume checkpoint)" checkbox changes nothing (at least with running VMs) because the default method is "Saved state":
Q1: if the default method is "Saved state" and my VMs are running what should I do to take a backup by using
"Child VM Snapshot" method?
Q2: is there any difference between a backup created by method 1 and method 2?
Thank you in advance,
Michael

Answer 1

Hi,
The two backup mechanisms used in the different backup scenario:
Short to say is:
Perform a backup from the server running Hyper-V
(host).
Perform a backup from
within the guest operating system of a virtual machine.
The detail explain is:
There are two basic methods you can use to perform a backup. You can:
Perform a backup from the server running Hyper-V. We recommend that you use this method to perform a full server backup because it captures more data than the other method. If the backup application is compatible with Hyper-V and the Hyper-V
VSS writer, you can perform a full server backup that helps protect all of the data required to fully restore the server, except the virtual networks. The data included in such a backup includes the configuration of virtual machines, snapshots associated with
the virtual machines, and virtual hard disks used by the virtual machines. As a result, using this method can make it easier to recover the server if you need to, because you do not have to recreate virtual machines or reinstall Hyper-V. However, virtual networks
are not included in a full server backup. You will need to reconfigure the virtual networking by recreating the virtual networks and then reattaching the virtual network adapters in each virtual machine to the appropriate virtual network. As part of your backup
planning, make sure you document the configuration and all relevant settings of your virtual network if you want to be able to recreate it.
• Perform a backup from within the guest operating system of a virtual machine.
Use this method when you need to back up data from storage that is not supported by the Hyper-V VSS writer. When you use this method, you run a backup application from the guest operating system of the virtual machine. If you need to use this
method, you should use it in addition to a full server backup and not as an alternative to a full server backup. Perform a backup from within the guest operating system before you perform a full backup of the server running Hyper-V. For more information about
storage considerations, see the following section.
The related KB:
Planning for Backup
http://technet.microsoft.com/en-us/library/dd252619(v=ws.10).aspx
Hope this helps.
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